/Engine/Source/Runtime/AdvancedWidgets/Public/Framework/PropertyViewer/IFieldExpander.h
the struct that can be expanded from the function. ie. This can be the function itself (to see the arguments) or a return property.
virtual [TOptional](API\Runtime\Core\IO\TOptional)< const [UStruct](API\Runtime\CoreUObject\UObject\UStruct) * > GetExpandedFunction ( const [UFunction](API\Runtime\CoreUObject\UObject\UFunction) * Function ) const